Electric hand-held hair cutting appliances come in a number of different forms depending on the intended use of the appliance, such as for trimming facial or body hair, clipping the hair on one's head or on a pet, or for shaving facial or body hair. Such hair cutting appliances typically have at least one stationary blade and at least one reciprocating blade operatively connected to an eccentric drive assembly such that rotation of the drive assembly linearly reciprocates the reciprocating blade relative to the stationary blade. It is common for the drive assembly to be housed in a handle of the appliance while the reciprocating blade and stationary blade comprise part of a blade head assembly that is removably attachable to the handle to permit cleaning and replacement of the blade head assembly. It is also now common for hair cutting appliances to be sold as kits that include a single handle having the drive assembly therein, and interchangeable blade head assemblies wherein the blade head assemblies have different size reciprocating blades or are otherwise configured for different purposes.
During operation of these hand-held hair cutting appliances, the linear reciprocation of the reciprocating blade often generates an inertial moment within the appliance that results in the appliance vibrating within the user's hand. Depending on the particular location of the center of mass of the reciprocating blade relative to the point of driving connection with the drive assembly, substantial vibration may occur.
Attempts to reduce the vibration level have revolved around providing counter weight on the rotating eccentric drive assembly to counter balance the vibration caused by the reciprocating cutting blade. While this can reduce vibration of the system in the direction of reciprocating blade movement, it creates vibration in other directions. In addition, because the counter weight is retained in the handle, it is adapted only to counter-balance one particular blade head assembly arrangement. For example, for appliances that are intended to be used with multiple interchangeable blade head assemblies, the reciprocating cutting blades of the different blade assemblies are typically of different mass and/or location within the respective assemblies and thus the center of mass of such blades varies from one blade head assembly to the next. As such, providing a counter weight on the drive assembly in the handle may reduce vibration only for the blade head assembly to which the counter weight arrangement corresponds. When other blade head assemblies are used (e.g., having different size, mass, etc.), the counter weight arrangement in the handle is no longer tuned to the particular blade head assembly being used and the benefits of the counter weight arrangement are substantially lost.
There is a need, therefore, for an electrically operated hand-held hair cutting appliance with an improved counter weight system to reduce vibration during use.